Known gas-blast circuit-breakers such as illustrated in FIG. 1 include two arc-extinguishing chambers 1 and 2 connected together in series by a live central casing 3, the assembly being set on a ceramic insulating support 4 which rests on a base 5 which includes a supply of compressed gas. Each of the chambers includes contacts 6 and 7 between which the electric arc is generated when they open, a set of main valves 8 and an auxiliary valve 9. Rods 10 operate one of the valves 8 as well as the contacts 6 and 7 of the circuit-breaker; these rods are actuated from the ground by electrically operated valves.
It is known to use compensated force valves with two seats as gas-blast valves, said valves including two pistons integral with each other which are subject to a pressure difference allowing an operation which requires only a relatively small force.
However, earlier arrangements were designed to operate with control valves actuated by mechanical rods and release valves operated by gas-blast and required relatively large exhaust passages between the two valves. This disposition impairs the rapidity of the control means and it is known that to open a circuit-breaker, the valve must be controlled in the shortest time possible, approximately 30 milliseconds being prohibitive at very high voltages in conventional arrangements. Further, after operation, the return of the control means to a position which allows further operation must also be carried out in a fairly short time, this not being the case with conventional arrangements, which are also subjected to the forces generated by the expansion of the control rods and this affects the operation of the valve.
The valve in accordance with the present invention tends to remedy the above-mentioned drawbacks and groups together in a single arrangement the functions of both valves of the prior art. It reduces the activation time to 10 milliseconds. The return of the control means is also carried out in a very short time. The operation of the arrangement is independent of any expansion of the control rods. Lastly sufficient damping of the movement of the moving parts of the valve control means is provided.